Boost surging and N75 Valve replacement / adjustment
03-18-2004, 11:18 AM
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Boost surging and N75 Valve replacement / adjustment
Just thought I would share my experience with boost surging and adjusting/replacing the N75 to cure this problem.
I was using a 1.3 bar Neuspeed chip program and the car was running great. It went in for an RS4 clutch replacement / rear main seal R/R back in January. I've been driving the car pretty easy for the past month breaking the clutch in. Recently (driving the car harder now) I noticed that the boost would peak about 1.2-1.3 bar then drop to .8 bar, then back to 1.2 then drop to 1.0 and then back to 1.2, you get the picture (surging).
After searching the archives, I found that the culprit may be the N75 valve. I didn't even mess with adjusting my original (84K miles on it). I purchased a new one and installed it (very basic install). I test drove the car however the surging was still present.
I marked the "factory" position of the screw on the N75 with a Sharpie. I then turned the screw a 1/4 turn clockwise. Miraculously, this fixed my surging issue, however I was only boosting about 1.1 bar tapering to .9-1.0 I then marked this position and adjusted it back an 1/8 of a turn counter-clockwise. The car runs perfect, 1.3 bar tapering to 1.1
Thanks to VonK and others who have posted about the N75 and explained how it works with the 2.7T engine. I found these posts very informative and it saved me a lot of time troubleshooting this issue.
I was using a 1.3 bar Neuspeed chip program and the car was running great. It went in for an RS4 clutch replacement / rear main seal R/R back in January. I've been driving the car pretty easy for the past month breaking the clutch in. Recently (driving the car harder now) I noticed that the boost would peak about 1.2-1.3 bar then drop to .8 bar, then back to 1.2 then drop to 1.0 and then back to 1.2, you get the picture (surging).
After searching the archives, I found that the culprit may be the N75 valve. I didn't even mess with adjusting my original (84K miles on it). I purchased a new one and installed it (very basic install). I test drove the car however the surging was still present.
I marked the "factory" position of the screw on the N75 with a Sharpie. I then turned the screw a 1/4 turn clockwise. Miraculously, this fixed my surging issue, however I was only boosting about 1.1 bar tapering to .9-1.0 I then marked this position and adjusted it back an 1/8 of a turn counter-clockwise. The car runs perfect, 1.3 bar tapering to 1.1
Thanks to VonK and others who have posted about the N75 and explained how it works with the 2.7T engine. I found these posts very informative and it saved me a lot of time troubleshooting this issue.
03-18-2004, 11:49 AM
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zapco was one of the , if not the 1st to post that info here
afaik
I like how vonk always summarizes what everyone else has already posted and gets credit for it hah
oh well pointless post
I like how vonk always summarizes what everyone else has already posted and gets credit for it hah
oh well pointless post
03-18-2004, 11:49 AM
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When did Neuspeed come out with their 1.3 bar chip? Have any logs?
Also, does Neuspeed have a policy about trying the chip prior to purchase like other tuners? I'd love to compare the chip to X 
03-18-2004, 11:55 AM
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Could you be experiencing throttle cut? WOLSCOD and I are running a protoype solution...
to throttle cut which is working fantastically. It allows you to control the boost spike precisely and it eliminates hesitiation.